I recently bought the Phoenix R/C simulator. It comes with its own USB-cable to plug into your remote controller’s trainer cable. A friend of mine has a Spektrum remote, and the stereo 3.5mm jack plugs right is.

I have a Futaba FF9 remote, so they wanted me to buy the “adapter cable to FF9” for €16. Since I already had the pinout of the FF9-connector figured out, I figured I could make this cable myself.

Since the FF9 connectors are hard to find, I wanted to reuse the one I have. So I worked out a wiring scheme that would allow me to connect pretty much everything to everything.

The standardized interface

I chose an RJ45-jack (officially called 8P8C), since they’re easy and cheap. I got my inspiration from the RS232-over-RJ45 idea:

  1. not connected
  2. not connected
  3. ground (output)
  4. signal out
  5. signal in
  6. ground (input)
  7. sim signal
  8. sim signal

I numbered the connector ((c) David Monniaux) from right to left, but as long as you are consistent it should work. The two sim signals are shorted on the slave-side. On my FF9, that activates simulator mode: switch on the device, but without HF-transmitter on.

Note that by simply crossing over the pins, the output is fed into the input of the other remote. My “master-slave” cable does this crossing for pins 3, 4, 5 and 6; it also shorts pins 7-8 on the slave-side.

FF9 pinout

My FF9-cable now looks like this:

  1. not connected
  2. ground – connected to RJ45 pins 3 and 6
  3. signal out – connected to RJ45 pin 4
  4. sim signal – connected to RJ45 pin 7
  5. sim signal – connected to RJ45 pin 8
  6. signal in – connected to RJ45 pin 5

Phoenix pinout

The phoenix cable terminates on an 3.5mm male mini stereo jack ((c) Dinesh Pratap Singh) (officially TRS connector). So I tied together a female socket and an RJ45 connector:

  • sleeve – ground – connected to RJ45 pins 3 and 6
  • ring – ??? – not connected
  • tip – signal in – connected to RJ45 pin 5


  1. Roly says:

    Thanks for the info. I want to make the Phoenix USB cable for my Spektrum DX4e. I thought I could butcher an old USB cable and put a 3.5mm jack on one end. Any chance of you telling what the pin-out match-up is for the USB and 3.5mm jack ends of the Phoenix cable ?
    Thanks in advance.

  2. Niobos says:


    The Phoenix USB interface acts as a kind of dongle, so there is a microchip in between the USB and the 3.5mm jack side. And even technically speaking, it will not be possible to just map USB-pins to 3.5mm pins.
    If you do want to make your cable yourself, I would recommend you to take a look at SmartPropoPlus, which uses the line-in of your sound card to read the Tx.